Fin field effect transistor and method of manufacturing the same

ABSTRACT

Provided are a FinFET and a method of manufacturing the same. A FinFET may include at least one active fin, at least one gate insulating layer pattern, a first electrode pattern, a second electrode pattern and at least one pair of source/drain expansion regions. The at least one active fin may be formed on a substrate. The at least one gate insulating layer pattern may be formed on the at least one active fin. The first electrode pattern may be formed on the at least one gate insulating layer pattern. Further, the first electrode pattern may be intersected with the at least one active fin. The second electrode pattern may be formed on the first electrode pattern. Further, the second electrode pattern may have a width greater than that of the first electrode pattern. The at least one pair of source/drain expansion regions may be formed on a surface of the at least one active fin on both sides of the first electrode pattern. Thus, the FinFET may have improved capacity and reduced GIDL current.

PRIORITY STATEMENT

This application claims priority under 35 U.S.C. §119 to Korean PatentApplication No. 2007-88162, filed on Aug. 31, 2007, in the KoreanIntellectual Property Office (KIPO), the entire contents of which areherein incorporated by reference.

BACKGROUND

1. Field

Example embodiments relate to a field effect transistor, and a method ofmanufacturing the same. Other example embodiments relate to a fin fieldeffect transistor (FinFET), and a method of manufacturing the FinFET.

2. Description of the Related Art

In order to provide semiconductor devices with a more rapid operationalspeed and increased integration degree, a channel length of a MOS fieldeffect transistor (MOSFET) has been gradually reduced. However, in aplanar MOSFET, an electrical field may affect the planar MOSFET by adrain voltage because the channel length may become shorter. Further,this may cause a short channel effect where a channel drive capacity maybe deteriorated due to a gate electrode. To control a threshold voltageof the planar MOSFET, increasing an impurity concentration of a channelmay be required. However, this may cause relatively low mobility ofcarriers and a relatively low current drive force. Therefore, in theplanar MOSFET, suppressing the short channel effect may be difficultbecause the planar MOSFET may have a more rapid operational speed and anincreased integration degree.

A type of transistors, which have a structure capable of reducing theshort channel effect, may include a fin field effect transistor(FinFET). The FinFET may include an active region having athree-dimensional fin shape. The fin may be surrounded by a gateelectrode. Thus, a three-dimensional channel may be formed along asurface of the fin. Because the channel is formed on an upper surfaceand sidewalls of the fin, the FinFET may have a larger effect channelwidth in a relatively small horizontal area. Thus, a semiconductordevice having the FinFET may have a relatively small size and a morerapid operational speed. Further, the short channel effect may bereduced owing to a reduced capacitance of the drain region. In order toimprove operational characteristics of the FinFET, uniformly formingsource/drain regions on a surface of the three-dimensional fin may benecessary. However, because a body width of the fin is graduallynarrowed and the fin has the three-dimensional shape, the surface of thefin may not be readily doped with impurities.

Further, the FinFET may have a gate induced drain leakage (GIDL) currenthigher than that of the planar MOSFET. This may be caused by thethree-dimensional shape of the fin that may provide a relatively largeoverlapped area between the gate electrode and the drain region. Todecrease the GIDL current, minimizing or reducing the overlapped areabetween the source/drain regions and the gate electrode may be required.However, a process for forming the source/drain regions may includedoping impurities, and activating the impurities by a thermal treatment.The thermal treatment may cause a horizontal and vertical diffusion ofthe impurities. The diffusion of the impurities may cause a continuousincrease of the overlapped area between the source/drain regions and thegate electrode. As a result, the GIDL current may not be sufficientlyreduced.

In a conventional method of reducing the GIDL current, after forming thegate electrode, an offset spacer may be formed on a sidewall of the gateelectrode to reduce the overlapped area between the source/drain regionsand the gate electrode. However, the offset spacer may be formed on asidewall of the fin to be doped with the impurities as well as thesidewall of the gate electrode. Thus, the impurities in the sidewall ofthe fin, where the offset spacer is formed, may be different from thosein the upper surface of the fin where the offset spacer may not beformed. Further, a higher energy to dope the sidewall of the fin withthe impurities through the offset spacer may be required which causesdamages to the surface of the fin.

SUMMARY

Example embodiments provide a fin field effect transistor (FinFET) thatis capable of reducing a gate induced drain leakage (GIDL) current withincreased capacity. Example embodiments also provide a method ofmanufacturing the above-mentioned FinFET.

According to example embodiments, a FinFET may include at least oneactive fin, at least one gate insulating layer pattern, a firstelectrode pattern, a second electrode pattern and at least one pair ofsource/drain expansion regions. The at least one active fin may beformed on a substrate. The at least one gate insulating layer patternmay be formed on the at least one active fin. The first electrodepattern may be formed on the at least one gate insulating layer pattern.Further, the first electrode pattern may be intersected with the atleast one active fin. The second electrode pattern may be formed on thefirst electrode pattern. Further, the second electrode pattern may havea width greater than that of the first electrode pattern. The at leastone pair of source/drain expansion regions may be formed on a surface ofthe active fin on both sides of the first electrode pattern.

According to example embodiments, the first electrode pattern and thesecond electrode pattern may have materials having different etchingselectivities. The first electrode pattern may include polysilicongermanium. The second electrode may include polysilicon. The firstelectrode pattern and the second electrode pattern may be doped withimpurities having a conductive type substantially the same as that ofimpurities in the source/drain expansion regions. Alternatively, thefirst electrode pattern may include titanium, titanium nitride, tantalumand/or tantalum nitride. The second electrode pattern may includepolysilicon.

According to example embodiments, the first electrode pattern may have athickness of about 100 Å to about 400 Å. According to exampleembodiments, the FinFET may further include spacers on sidewalls of thefirst electrode pattern and a second electrode pattern, and source/drainregions in a surface of the active fin on both sides of each of thespacers. The source/drain regions may have an impurity concentrationhigher than that of the at least one pair of source/drain expansionregions.

According to example embodiments, the FinFET may further include anisolation layer pattern on the substrate on both sides of the at leastone active pin. According to example embodiments, the at least onesource/drain expansion region may be overlapped with an end of the firstelectrode pattern. According to example embodiments, the substrate mayinclude a single crystalline silicon substrate, a silicon-on-insulator(SOI) substrate, a silicon germanium-on-insulator (SGOI) substrate, or agermanium-on-insulator (GOI) substrate.

According to example embodiments, the at least one active fin mayinclude first and second active fins in an NMOS region and a PMOS regionof the substrate, respectively, the at least one gate insulating layerpattern may include first and second gate insulating layer patterns on asurface of the first and second active fins, respectively, the at leastone pair of source/drain expansion regions may include first and secondsource/drain expansion regions, and the FinFET may include the firstsource/drain expansion region in the surface of the first active fin onboth sides of the first electrode pattern, the first source/drainexpansion regions doped with n-type impurities, a third electrodepattern on the second gate insulating layer pattern, the third electrodepattern being intersected with the second active fin, a fourth electrodepattern on the third electrode pattern, the fourth electrode patternhaving a width greater than that of the third electrode pattern, and thesecond source/drain expansion regions in the surface of the secondactive fin on both sides of the third electrode pattern, the secondsource/drain expansion regions doped with p-type impurities.

Furthermore, the third electrode pattern may include a materialsubstantially the same as that of the first electrode pattern. Thefourth electrode pattern may be formed on the third electrode pattern.Further, the fourth electrode pattern may have a width greater than thatof the third electrode pattern. The second source/drain expansionregions may be formed in a surface of the second active fin on bothsides of the third electrode pattern. Further, the second source/drainregions may be doped with p-type impurities.

According to example embodiments, the first electrode pattern and thesecond electrode pattern may have different work functions. The firstelectrode pattern may include polysilicon germanium doped with n-typeimpurities. The third electrode pattern may include polysilicongermanium doped with p-type impurities. Alternatively, the firstelectrode pattern and the second electrode pattern may havesubstantially the same work function of about 4.0 eV to about 5.2 eV.The first electrode pattern and the third electrode pattern may includetitanium, titanium nitride, tantalum and/or tantalum nitride.

In a method of manufacturing a FinFET in accordance with exampleembodiments, an active fin may be formed on a substrate. A gateinsulating layer pattern may be formed on the active fin. A firstelectrode layer and a second electrode layer may be sequentially formedon the gate insulating layer pattern. The first electrode layer and thesecond electrode layer may be patterned to form a first preliminaryelectrode pattern and a second electrode pattern. The first preliminaryelectrode pattern may be intersected with the active fin. Impurities maybe implanted into a surface of the active fin on both sides of the firstpreliminary electrode pattern and the second electrode pattern to formsource/drain expansion regions. A sidewall of the first preliminaryelectrode pattern may be partially removed to form a first electrodepattern having a width less than that of the second electrode pattern.

According to example embodiments, the first electrode layer and thesecond electrode layer may have materials having different etchingselectivities. The first electrode layer may include polysilicongermanium. The second electrode layer may include polysilicon. Inexample embodiments, patterning the first electrode layer and the secondelectrode layer may include forming a mask pattern on the secondelectrode pattern, dry-etching the second electrode layer using the maskpattern as an etch mask to form the second electrode pattern, andwet-etching the first electrode layer under the second electrode patternto form the first preliminary electrode pattern.

The first electrode layer may be wet-etched using an etching solutionthat may include nitric acid, fluoric acid, acetic acid and deionizedwater. According to example embodiments, partially removing the sidewallof the first preliminary electrode pattern may include a wet etchingprocess using an etching solution. The etching solution may includeammonium hydroxide, hydrogen peroxide and deionized water.Alternatively, the etching solution may include nitric acid, fluoricacid, acetic acid and deionized water. Alternatively, the firstelectrode layer may include titanium, titanium nitride, tantalum and/ortantalum nitride. The second electrode layer may include polysilicon.

According to example embodiments, forming the first electrode patternmay include partially etching the first preliminary electrode pattern tooverlap the first electrode pattern with an end of the source/drainexpansion regions. According to example embodiments, forming thesource/drain expansion regions may include a plasma ion implantationprocess and/or a tilt-angle ion implantation process. According toexample embodiments, the method may further include forming spacers onsidewalls of the first electrode pattern and a second electrode pattern,and doping a surface of the active fin on both sides of each of thespacers with impurities to form source/drain regions. Forming thesource/drain regions may include a plasma ion implantation processand/or a tilt-angle ion implantation process.

In a method of manufacturing a FinFET in accordance with exampleembodiments, an active fin protruded from a substrate may be formed. Agate insulating layer pattern may be formed on a surface of the activefin. A first electrode layer and a second electrode layer may besequentially formed on the gate insulating layer pattern. The secondelectrode layer may be patterned to form a second electrode pattern, thesecond electrode pattern being intersected with the active fin. Thefirst electrode layer exposed by the second electrode pattern may beetched to form a first preliminary electrode pattern. A sidewall of thefirst preliminary electrode pattern may be partially etched to form afirst electrode pattern having a width less than that of the secondelectrode pattern. The surface of the active fin exposed by the firstelectrode pattern and the second electrode pattern may be doped to formsource/drain expansion regions.

According to example embodiments, the first preliminary electrodepattern and the first electrode pattern may be formed by a wet etchingprocess. According to example embodiments, the method may furtherinclude partially removing the sidewall of the first electrode patternto reduce an overlapped area between the first electrode pattern and thesource/drain expansion regions.

In a method of manufacturing a FinFET in accordance with exampleembodiments, a first active pin may be formed in an NMOS region of asubstrate. A second active pin may be formed in a PMOS region of thesubstrate. A first gate insulating layer pattern may be formed on thefirst active fin. A second oxide layer pattern may be formed on thesecond active fin. A first electrode layer may be formed on the firstgate insulating layer pattern. A second electrode layer may be formed onthe first electrode pattern. The first electrode layer and the secondelectrode layer may be patterned to form a first preliminary electrodepattern, a second electrode pattern, a third preliminary electrodepattern and a fourth electrode pattern. The first preliminary electrodepattern may be intersected with the first active fin. The thirdpreliminary electrode pattern may be intersected with the second activefin. N-type impurities may be implanted into a surface of the firstactive fin on both sides of the first preliminary electrode pattern andthe second electrode pattern. P-type impurities may be implanted into asurface of the second active fin on both sides of the third preliminaryelectrode pattern and the fourth electrode pattern. Sidewalls of thefirst preliminary electrode pattern and the third preliminary electrodepattern may be partially removed to form a first electrode pattern and athird electrode pattern.

According to example embodiments, the FinFET may have the source/drainexpansion regions having a uniform doping concentration in the surfaceof the active fin. Thus, the FinFET may have improved capacity. Further,the source/drain expansion regions may not excessively infiltrate intoan edge of the first electrode pattern. Therefore, the areas of the gateelectrode and the source/drain expansion regions may not overlap witheach other much, so that the GIDL current may be reduced.

BRIEF DESCRIPTION OF THE DRAWINGS

Example embodiments will be more clearly understood from the followingdetailed description taken in conjunction with the accompanyingdrawings. FIGS. 1-17 represent non-limiting, example embodiments asdescribed herein.

FIG. 1 is a perspective view illustrating a FinFET in accordance withexample embodiments;

FIG. 2 is a cross-sectional view take along a line I-I′ in FIG. 1;

FIGS. 3 to 13 are perspective views and cross-sectional viewsillustrating a method of manufacturing the FinFET in FIGS. 1 and 2 inaccordance with example embodiments;

FIGS. 14 to 16 are perspective views and cross-sectional viewsillustrating a method of manufacturing the FinFET in FIGS. 1 and 2 inaccordance with example embodiments; and

FIG. 17 is a perspective view illustrating a CMOS FinFET in accordancewith example embodiments.

It should be noted that these Figures are intended to illustrate thegeneral characteristics of methods, structure and/or materials utilizedin certain example embodiments and to supplement the written descriptionprovided below. These drawings are not, however, to scale and may notprecisely reflect the precise structural or performance characteristicsof any given embodiment, and should not be interpreted as defining orlimiting the range of values or properties encompassed by exampleembodiments. For example, the relative thicknesses and positioning ofmolecules, layers, regions and/or structural elements may be reduced orexaggerated for clarity. The use of similar or identical referencenumbers in the various drawings is intended to indicate the presence ofa similar or identical element or feature.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

Example embodiments are described more fully hereinafter with referenceto the accompanying drawings, in which example embodiments are shown.Example embodiments may, however, be embodied in many different formsand should not be construed as limited to example embodiments set forthherein. Rather, these example embodiments are provided so that thisdisclosure will be thorough and complete, and will fully convey thescope of example embodiments to those skilled in the art. In thedrawings, the sizes and relative sizes of layers and regions may beexaggerated for clarity.

It will be understood that when an element or layer is referred to asbeing “on,” “connected to” or “coupled to” another element or layer, itcan be directly on, connected or coupled to the other element or layeror intervening elements or layers may be present. In contrast, when anelement is referred to as being “directly on,” “directly connected to”or “directly coupled to” another element or layer, there are nointervening elements or layers present. Like numerals refer to likeelements throughout. As used herein, the term “and/or” includes any andall combinations of one or more of the associated listed items.

It will be understood that, although the terms first, second, third etc.may be used herein to describe various elements, components, regions,layers and/or sections, these elements, components, regions, layersand/or sections should not be limited by these terms. These terms areonly used to distinguish one element, component, region, layer orsection from another region, layer or section. Thus, a first element,component, region, layer or section discussed below could be termed asecond element, component, region, layer or section without departingfrom the teachings of example embodiments.

Spatially relative terms, such as “beneath,” “below,” “lower,” “above,”“upper” and the like, may be used herein for ease of description todescribe one element or feature's relationship to another element(s) orfeature(s) as illustrated in the figures. It will be understood that thespatially relative terms are intended to encompass differentorientations of the device in use or operation in addition to theorientation depicted in the figures. For example, if the device in thefigures is turned over, elements described as “below” or “beneath” otherelements or features would then be oriented “above” the other elementsor features. Thus, the exemplary term “below” can encompass both anorientation of above and below. The device may be otherwise oriented(rotated 90 degrees or at other orientations) and the spatially relativedescriptors used herein interpreted accordingly.

The terminology used herein is for the purpose of describing particularexample embodiments only and is not intended to be limiting of exampleembodiments. As used herein, the singular forms “a,” “an” and “the” areintended to include the plural forms as well, unless the context clearlyindicates otherwise. It will be further understood that the terms“comprises” and/or “comprising,” when used in this specification,specify the presence of stated features, integers, steps, operations,elements, and/or components, but do not preclude the presence oraddition of one or more other features, integers, steps, operations,elements, components, and/or groups thereof.

Example embodiments are described herein with reference tocross-sectional illustrations that are schematic illustrations ofidealized example embodiments (and intermediate structures). As such,variations from the shapes of the illustrations as a result, forexample, of manufacturing techniques and/or tolerances, are to beexpected. Thus, example embodiments should not be construed as limitedto the particular shapes of regions illustrated herein but are toinclude deviations in shapes that result, for example, frommanufacturing. For example, an implanted region illustrated as arectangle will, typically, have rounded or curved features and/or agradient of implant concentration at its edges rather than a binarychange from implanted to non-implanted region. Likewise, a buried regionformed by implantation may result in some implantation in the regionbetween the buried region and the surface through which the implantationtakes place. Thus, the regions illustrated in the figures are schematicin nature and their shapes are not intended to illustrate the actualshape of a region of a device and are not intended to limit the scope ofexample embodiments.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which example embodiments belong. Itwill be further understood that terms, such as those defined in commonlyused dictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of the relevant art andwill not be interpreted in an idealized or overly formal sense unlessexpressly so defined herein. Hereinafter, some example embodiments willbe explained in detail with reference to the accompanying drawings.

FIG. 1 is a perspective view illustrating a FinFET in accordance withexample embodiments, and FIG. 2 is a cross-sectional view take along aline I-I′ in FIG. 1. Referring to FIGS. 1 and 2, an active fin 102 maybe formed on a semiconductor substrate 100. The semiconductor substrate100 may include a single crystalline silicon substrate, asilicon-on-insulator (SOI) substrate, a silicon germanium-on-insulator(SGOI) substrate and/or a germanium-on-insulator (GOI) substrate. Inexample embodiments, the semiconductor substrate 100 may include thesingle crystalline silicon substrate. The active fin 102 may havea'shape extending in a first direction. In example embodiments, theactive fin 102 may include single crystalline silicon.

Isolation layer patterns 101 may be arranged on both sides of the activefin 102. The active fin 102 may have an upper surface higher than thatof the isolation layer patterns 101. Thus, the active fin 102 may beprotruded from the upper surface of the isolation layer patterns 101. Inexample embodiments, the protruded height of the active fin 102 from theisolation layer patterns 101 may be less than a width of the uppersurface of the active fin 102, e.g., a width of a fin body in the activefin 102. Alternatively, as shown in the drawings, the protruded heightof the active fin 102 from the isolation layer patterns 101 may besubstantially the same as the width of the upper surface of the activefin 102.

A gate insulating layer pattern 104 may be formed on the upper surfaceof the active fin 102. In example embodiments, the gate insulating layerpattern 104 may be formed by a thermal oxidation process using siliconoxide. A first electrode pattern 106 b may be formed on the gateinsulating layer pattern 104. The first electrode pattern 106 b may beintersected with the active fin 102. The first electrode pattern 106 bmay serve as a gate electrode of the FinFET. Thus, a threshold voltageof the FinFET may vary in accordance with a work function of the firstelectrode pattern 106 b.

Therefore, the first electrode pattern 106 b may include a materialsuitable for a gate electrode of an N type transistor or a P typetransistor. For example, the first electrode pattern 106 b may include aconductive material having a work function that may be controlled bydoping impurities. Alternatively, the first electrode pattern 106 b mayinclude a conductive material having a mid-gap work function that may bea middle value of work functions of the gate electrodes of the N typetransistor and the P type transistor. In example embodiments, themid-gap work function may include a work function of about 4.0 eV toabout 5.2 eV.

For example, the first electrode pattern 106 b may include polysilicongermanium. The polysilicon germanium may be doped with impurities havinga conductive type substantially the same as that of impurities insource/drain regions. When the FinFET is P type, the polysilicongermanium may be doped with p-type impurities, e.g., boron. In contrast,when the FinFET is N type, the polysilicon germanium may be doped withn-type impurities, e.g., arsenic and/or phosphorous.

Alternatively, the first electrode pattern 106 b may include titanium,titanium nitride, tantalum and/or tantalum nitride. These may be usedalone or in a combination thereof. The above-mentioned metals may havethe mid-gap work function so that the metal may be used for the gateelectrodes of the N type transistor and the P type transistor. When thefirst electrode pattern 106 b has a thickness of below about 100 Å, thefirst electrode pattern 106 b may not sufficiently function as the gateelectrode. In contrast, when the first electrode pattern 106 b has athickness of above about 400 Å, an etching process may not be readilycontrolled. Thus, the first electrode pattern 106 b may have a thicknessof about 100 Å to about 400 Å, for example, about 300 Å.

A second electrode pattern 108 a may be formed on the first electrodepattern 106 b. In example embodiments, the second electrode pattern 108a may have a width greater than that of the first electrode pattern 106b. For example, a structure including the first electrode pattern 106 band the second electrode pattern 108 a sequentially stacked may have a“T” shape. Thus, the second electrode pattern 108 a may have a shapeconfigured to fully cover an upper surface of the first electrodepattern 106 b.

The second electrode pattern 108 a may function so as to reduce aresistance of the gate electrode. For example, when the gate electrodeincludes only the first electrode pattern 106 b, the gate electrode mayhave a relatively high resistance because the first electrode pattern106 b may have be relatively thin, e.g., about 100 Å to about 400 Å.Thus, the gate electrode may have a reduced resistance by stacking thesecond electrode pattern 108 a on the first electrode pattern 106 b.

In example embodiments, the second electrode pattern 108 a may include amaterial having an etching selectivity with respect to a material of thefirst electrode pattern 106 b. For example, the second electrode pattern108 a may include a material that may not be etched much in a processfor etching the first electrode pattern 106 b. Further, the secondelectrode pattern 108 a may include a material having relatively strongadhesion strength with respect to the first electrode pattern 106 b.Furthermore, the second electrode pattern 108 a may include a materialthat may be readily etched using an etching gas.

For example, the second electrode pattern 108 a may include polysilicon.Further, the polysilicon may be doped with impurities having aconductive type substantially the same as that of the impurities in thesource/drain regions. Alternatively, the second electrode pattern 108 amay include a metal, e.g., tungsten. Further, although not depicted inthe drawings, the second electrode pattern 108 a may have a structurewhere a polysilicon layer pattern and a metal pattern or a metalsilicide layer pattern may be sequentially stacked.

Source/drain expansion regions 110 may be formed in a surface of thesemiconductor substrate 100 under the surface of the active fin 102 onboth sides of the first electrode pattern 106 b. In example embodiments,the source/drain expansion regions 110 may have an end partiallyoverlapped with both ends of the first electrode pattern 106 b.Alternatively, the end of each of the source/drain expansion regions 110may make contact with both ends of the first electrode pattern 106 b.However, the width of the first electrode pattern 106 b may be less thanthat of the second electrode pattern 108 a, and an overlapped areabetween the first electrode pattern 106 b and the source/drain expansionregions 110 may be reduced. Thus, a gate induced drain leakage (GIDL)current, which may be generated by a relatively large overlapped areabetween the first electrode pattern 106 b and the source/drain expansionregions 110, may be decreased.

Spacers 112 may be formed on sidewalls of the first electrode pattern106 b and the second electrode pattern 108 a. In example embodiments,the spacers 112 may include silicon nitride. Source/drain regions 114may be formed in the surface of the semiconductor substrate 100 underthe active fin 102 on both sides of the spacers 112. The source/drainregions 114 may have an impurity concentration higher than that of thesource/drain expansion regions 110.

FIGS. 3 to 13 are perspective views and cross-sectional viewsillustrating a method of manufacturing the FinFET in FIGS. 1 and 2 inaccordance with example embodiments. Referring to FIG. 3, asemiconductor substrate 100 including single crystalline silicon may beprocessed to form an active fin 102 protruded from an upper surface ofisolation layer patterns 101. Hereinafter, a process for forming theactive fin 102 may be illustrated in detail. An etch mask pattern (notshown) may be formed the semiconductor substrate 100 to selectivelycover a region of the semiconductor substrate 100 where the active fin102 may be formed. The semiconductor substrate 100, except for theregion, may be etched using the etch mask pattern to form isolationtrenches (not shown). An insulating layer (not shown) may be formed onthe semiconductor substrate 100 to fill the trenches. The insulatinglayer may be planarized until an upper surface of the etch mask patternmay be exposed to form preliminary isolation layers in the trenches.

Upper portions of the preliminary isolation layers may be partiallyetched to form the isolation layer patterns 101. By performing theabove-mentioned process, side faces of the trenches may be exposed toform the active fin 102 protruding from the isolation layer patterns101. In example embodiments, the preliminary isolation layer may beremoved by a wet etching process. The etch mask pattern may then beremoved to expose an upper surface of the active fin 102.

Alternatively, the semiconductor substrate 100 may include asilicon-on-insulator (SOI) substrate, a silicon germanium-on-insulator(SGOI) substrate and/or a germanium-on-insulator (GOI) substrate. Inexample embodiments, the active fin 102 may be formed by a simplepatterning process. Referring to FIG. 4, a gate insulating layer pattern104 may be formed on a surface of the active fin 102. In exampleembodiments, the surface of the active fin 102 may be thermally oxidizedto form the gate insulating layer pattern 104 including silicon oxide. Athickness of the gate insulating layer pattern 104 may vary inaccordance with characteristics of a desired transistor.

Referring to FIG. 5, a first electrode layer 106 may be formed on thegate insulating layer pattern 104. In example embodiments, the firstelectrode layer 106 may have a thickness of about 100 Å to about 400 Å,for example, about 300 Å. Because the first electrode layer 106 may berelatively thin, the first electrode layer 106 may be formed along aprofile of the active fin 102. In example embodiments, the firstelectrode layer 106 may include polysilicon germanium. Alternatively,the first electrode layer 106 may include titanium, titanium nitride,tantalum and/or tantalum nitride. These may be used alone or in acombination thereof. A process for forming the first electrode layer 106using the polysilicon germanium may be explained in detail.

A silicon seed layer (not shown) may be formed on the gate insulatinglayer pattern 104 and the isolation layer patterns 101. The silicon seedlayer may include polysilicon and/or amorphous silicon. Further, thesilicon seed layer may have a thickness of no more than about 30 Å.Furthermore, the silicon seed layer may be formed by a low pressurechemical vapor deposition (LPCVD) process. The silicon seed layer mayserve as a seed for forming a polysilicon germanium layer by asubsequent process.

The polysilicon germanium layer may be formed on the silicon seed layerby an LPCVD process using a silicon source gas and a germanium sourcegas. For example, the silicon source gas may include SiH₄. The germaniumsource gas may include GeH₄. A carrier gas may include H₂. Further, theLPCVD process may be performed under a pressure of about 10 mTorr toabout 100 mTorr at a temperature of about 500° C. to about 600° C. Anatom concentration of silicon and germanium in the silicon germaniumlayer may be adjusted by controlling flow rates of the silicon sourcegas and the germanium source gas. In contrast, the first electrode layer106 may include titanium nitride. For example, the first electrode layer106 may be formed by a chemical vapor deposition (CVD) process and/or anatomic layer deposition (ALD) process, which may use a titanium sourcegas including TiCl₄ and a nitrogen source gas including NH₃.

Referring to FIG. 6, a second electrode layer 108 may be formed on thefirst electrode layer 106. In example embodiments, the second electrodelayer 108 may have an etching selectivity different from that of thefirst electrode layer 106. The second electrode layer 108 may beconverted into an electrode pattern for reducing a resistance of a gateelectrode by a following process. Thus, to sufficiently reduce theresistance of the gate electrode, the second electrode layer 108 may berelatively thick. In example embodiments, the second electrode layer 108may have an upper surface higher than that of the active fin 102.

Further, the second electrode layer 108 may include a material havingstronger adhesion strength with respect to the first electrode layer106. Further, the second electrode layer 108 may include a material thatmay be readily etched using an etching gas. In example embodiments, thesecond electrode layer 108 may include polysilicon. Alternatively, thesecond electrode layer 108 may include a metal that may be etched by adry etching process. For example, the second electrode layer 108 mayinclude tungsten. In example embodiments, an ohmic layer (not shown) anda metal barrier layer (not shown) may be formed between the firstelectrode layer 106 and the second electrode layer 108.

Although not depicted in the drawings, when the second electrode layer108 includes polysilicon, a metal layer (not shown) or a metal silicidelayer (not shown) may be further formed on the polysilicon layer toreduce the resistance of the gate electrode. After forming the secondelectrode layer 108, a polishing process may be performed on the secondelectrode layer 108 to planarize an upper surface of the secondelectrode layer 108.

Further, impurities may be implanted into the first electrode layer 106and the second electrode layer 108. In example embodiments, theimpurities may have a conductive type substantially the same as that ofimpurities in source/drain regions. For example, when the firstelectrode layer 106 includes polysilicon germanium, the FinFET may havea proper work function, which may provide a desired threshold voltage,by doping the impurities.

Referring to FIG. 7, a mask pattern (not shown) may be formed on thesecond electrode layer 108 to cover a region of the second electrodelayer 108 where the gate electrode may be formed. In exampleembodiments, the mask pattern may include a photoresist pattern and/or ahard mask pattern. Further, the mask pattern may have a linear shapeextending in a direction substantially perpendicular to an extendingdirection of the active fin 102. The second electrode layer 108 may beetched using the mask pattern as an etch mask to form a second electrodepattern 108 a. In example embodiments, the second electrode layer 108may be etched by a dry etching process.

Referring to FIG. 8, the first electrode layer 106 exposed by the secondelectrode pattern 108 a may be etched to form a first preliminaryelectrode pattern 106 a. When the first electrode layer 106 includespolysilicon or metal having a mid-gap work function, the first electrodelayer 106 may not be readily etched. For example, a relatively long timefor etching the first electrode layer 106 may be required including theabove-mentioned material by a dry etching process. Further, the activefin 102 may be damaged by performing the dry etching process. Thus, thefirst electrode layer 106 may be etched by a wet etching process.

In example embodiments, when the first electrode layer 106 includespolysilicon germanium, a wet etching process using an etching solutionwhich includes nitric acid, fluoric acid, acetic acid and deionizedwater may be performed on the first electrode layer 106 to form thefirst preliminary electrode pattern 106 a. Alternatively, when the firstelectrode layer 106 includes titanium nitride, a wet etching processusing sulfuric acid may be performed on the first electrode layer 106 toform the first preliminary electrode pattern 106 a.

As shown in the drawings, the first preliminary electrode pattern 106 aand the second electrode pattern 108 a may have a linear shape extendingin a direction substantially perpendicular to an extending direction ofthe active fin 102. Further, the gate insulating layer pattern 104 maybe exposed by the first preliminary electrode pattern 106 a and thesecond electrode pattern 108 a.

Referring to FIGS. 9 and 12, impurities may be implanted into a surfaceof the active fin 102 on both sides of the first preliminary electrodepattern 106 a and the second electrode pattern 108 a to formsource/drain expansion regions 110. In example embodiments, the impurityimplantation process may include a tilted angle implantation processand/or a plasma ion doping process.

The plasma ion doping process may include generating a plasma sheath onthe semiconductor substrate 100, and applying a voltage between an anodeand a cathode on which the semiconductor substrate 100 is placed. Theimpurities may cross the plasma sheath and then penetrate into thesemiconductor substrate 100. According to the plasma ion doping process,the source/drain expansion regions 110 having a shallow and uniformdoping depth may be formed in the surface of the active fin 102.

After implanting the impurities into the semiconductor substrate 100,performing an activation process for activating the impurities may berequired. The activation process may include thermally treating thesemiconductor substrate 100. Further, the activation process may beperformed by an additional thermal treatment process. Alternatively, theactivation process may be performed together with other processes wherea thermal treatment may be carried out. The impurities in thesource/drain expansion regions 110 may diffuse in a lateral directionduring the activation process, so that an area between the source/drainexpansion regions 110 and the first preliminary electrode pattern 106 aoverlaps.

According to a conventional method, in order to reduce the overlappedarea between a gate electrode and impurity regions, an offset spacer(not shown) may be formed on a sidewall of the gate electrode beforeimplanting impurities. However, the offset spacer may be formed on asidewall of an active fin as well as the sidewall of the gate electrode.Thus, because the impurities may penetrate into the active fin throughthe offset spacer and a gate insulating layer pattern, increased energyto dope the sidewall of the active fin with the impurities may berequired. Further, although the ion implantation process isaccomplished, the impurity may not be uniformly distributed in the uppersurface and the sidewall of the active fin.

In contrast, the method of example embodiments may not include a processfor forming the offset spacer before forming the source/drain expansionregions 110. Therefore, the active fin 102 on which the gate insulatinglayer pattern 104 having a uniform thickness is formed may be exposed bythe first preliminary electrode pattern 106 a and the second electrodepattern 108 a, so that the source/drain expansion regions 110 in thesurface of the active fin 102 may have a uniform doping depth. Further,the method of example embodiments may include simple processes becausethe complicated process for forming the offset spacer may not beperformed.

When the impurity implantation process is performed, the firstpreliminary electrode pattern 106 a and the second electrode pattern 108a may be doped with impurities having a conductive type substantiallythe same as that of the impurities in the source/drain expansion regions110. Referring to FIGS. 10 and 13, a sidewall of the first preliminaryelectrode pattern 106 a may be partially removed to form a firstelectrode pattern 106 b having a width less than that of the secondelectrode pattern 108 a.

The source/drain expansion regions 110 may be formed without performingthe process for forming the offset spacer on the sidewall of the firstpreliminary electrode pattern 106 a, so that the source/drain expansionregions 110 may extend under the first preliminary electrode pattern 106a. Thus, an overlapped area between the first preliminary electrodepattern 106 a and the source/drain expansion regions 110 may be larger.Therefore, the overlapped area between the first preliminary electrodepattern 106 a and the source/drain regions 110 may be reduced bypartially removing the sidewall of the first preliminary electrodepattern 106 a.

However, when the first electrode pattern 106 b is not overlapped withthe source/drain expansion regions 110 by etching the first preliminaryelectrode pattern 106 a, the FinFET may have a relatively low drivingcurrent and undesirable switching characteristics. Thus, overlapping thefirst electrode pattern 106 b with the source/drain expansion regions110 or contacting the first electrode pattern 106 with the source/drainexpansion regions 110 may be necessary. In example embodiments, thesidewall of the first preliminary electrode pattern 106 a may be removedby a wet etching process.

For example, when the first preliminary electrode layer 106 a includespolysilicon germanium, a wet etching process using an etching solution,which includes ammonium hydroxide, hydrogen peroxide and deionized wateror nitric acid, fluoric acid, acetic acid and deionized water, may beperformed on the first preliminary electrode layer 106 a to form thefirst electrode pattern 106 b. The etching solution including ammoniumhydroxide, hydrogen peroxide and deionized water may etch thepolysilicon germanium at a slower speed of about 20 Å/min. Therefore,the wet etching process may be controlled so as to remove a relativelythin portion of the first preliminary electrode layer 106 a.Alternatively, when the first preliminary electrode layer 106 a includestitanium nitride, a wet etching process using an etching solution, whichincludes sulfuric acid, may be performed on the first preliminaryelectrode pattern 106 a to form the first electrode pattern 106 b.

Referring to FIG. 11, an insulating layer (not shown) may be formed onprofiles of the first electrode pattern 106 b, the second electrodepattern 108 a and the gate insulating layer pattern 104. In exampleembodiments, the insulating layer may include silicon nitride formed byan LPCVD process. The insulating layer may be anisotropically etched toform spacers 112 on sidewalls of the first electrode pattern 106 b andthe second electrode pattern 108 a. Further, the spacers 112 may beformed on the sidewall of the active fin 102.

Impurities may be implanted into the semiconductor substrate 100 havingthe spacers 112 to form source/drain regions 114 (See FIG. 2). Inexample embodiments, the source/drain regions 114 may have an impurityconcentration higher than that of the source/drain expansion regions110. According to example embodiments, the FinFET may have a reducedoverlapped area between the gate electrode and the drain region. Thus,the GIDL current may be decreased. Further, the FinFET may include thesource/drain expansion regions having a uniform and shallow junctiondepth, so that the FinFET may have improved operational characteristics.

FIGS. 14 to 16 are perspective views and cross-sectional viewsillustrating a method of manufacturing the FinFET in FIGS. 1 and 2 inaccordance with example embodiments. A method of example embodiments mayinclude processes substantially the same as those illustrated withreference to FIGS. 3 to 13 except for a process sequence of the firstelectrode pattern and the source/drain expansion regions. Processessubstantially the same as those illustrated with reference to FIGS. 3 to6 may be performed to form the gate insulating layer pattern 104, thefirst electrode layer 106 and the second electrode layer 108 on theactive fin 102.

Referring to FIG. 14, a mask pattern (not shown) may be formed on thesecond electrode layer 108 to cover a region of the second electrodelayer 108 where a gate electrode may be formed. In example embodiments,the mask pattern may include a photoresist pattern and/or a hard maskpattern. Further, the mask pattern may have a linear shape extending ina direction substantially perpendicular to an extending direction of theactive fin 102. The second electrode layer 108 may be dry-etched usingthe mask pattern to form the second electrode pattern 108 a. In exampleembodiments, the second electrode layer 108 may be anisotropicallyetched by a dry etching process.

Referring to FIG. 15, the first electrode layer 106 exposed by thesecond electrode pattern 108 a may be wet-etched to form the firstelectrode layer pattern 106 b having a width less than that of thesecond electrode pattern 108 a. By the wet etching process, a portion ofthe first electrode layer 106 exposed by the second electrode pattern108 a may be initially etched. A sidewall of the first electrode layer106 may then be etched to form the first electrode pattern 106 b havingthe width less than that of the second electrode pattern 108 a.

In example embodiments, when the first electrode layer 106 includespolysilicon germanium, an etching solution for etching the firstelectrode layer 106 may include nitric acid, fluoric acid, acetic acidand deionized water or ammonium hydroxide, hydrogen peroxide anddeionized water. Alternatively, when the first electrode layer 106includes titanium nitride, an etching solution for etching the firstelectrode layer 106 may include sulfuric acid.

Referring to FIG. 16, impurities may be implanted into the semiconductorsubstrate 100 having the first electrode pattern 106 b and the secondelectrode pattern 108 a to form source/drain expansion regions 110 in asurface of the active fin 102. In example embodiments, the impurityimplantation process may include a tilted angle implantation processand/or a plasma ion doping process. The second electrode pattern 108 amay serve as an ion implantation mask in the impurity implantationprocess. Thus, the surface of the semiconductor substrate 100 on bothsides of the second electrode pattern 108 a may be mainly doped with theimpurities. As a result, although the impurities may diffuse, anoverlapped area between the first electrode pattern 106 b and thesource/drain expansion regions 110 may not be significantly increased.

Although not depicted in the drawings, after forming the source/drainexpansion regions 110, a process for partially removing a sidewall ofthe first electrode pattern 106 b may be additionally performed tofurther reduce the overlapped area between the first electrode pattern106 b and the source/drain expansion regions 110. Processessubstantially the same as those illustrated with reference to FIG. 11may be performed to complete the FinFET. For example, the spacers may beformed on sidewalls of the first electrode pattern 106 b, the secondelectrode pattern 108 a and the active fin 102. Impurities may beimplanted into the semiconductor substrate 100 to form source/drainregions. According to example embodiments, the first electrode patternmay be formed by one wet etching process. Thus, the FinFET may bemanufactured by the simple method.

FIG. 17 is a perspective view illustrating a CMOS FinFET in accordancewith example embodiments. Referring to FIG. 17, a semiconductorsubstrate 200 having an NMOS region and a PMOS region may be prepared. Afirst active fin 202 may be formed in the NMOS region of thesemiconductor substrate 200. A second active fin 204 may be formed inthe PMOS region of the semiconductor substrate 200. Isolation layerpatterns 201 may be arranged on both sides of the first active fin 202and the second active fin 204. Further, the isolation layer patterns 201may have an upper surface lower than that of the first active fin 202and the second active fin 204. Thus, the first active fin 202 and thesecond active fin 204 may protrude from the isolation layer patterns201.

A first gate insulating layer pattern 206 a may be formed on a surfaceof the first active fin 202. A second gate insulating layer pattern 206b may be formed on a surface of the second active fin 204. In exampleembodiments, the first gate insulating layer pattern 206 a and thesecond gate insulating layer pattern 206 b may include silicon oxideformed by a thermal oxidation process.

A first electrode pattern 208 a may be formed on the first gateinsulating layer pattern 206 a. The first electrode pattern 208 a may beintersected with the first active fin 202. Further, the first electrodepattern 208 a may have a first work function. In example embodiments,the first electrode pattern 208 a may include polysilicon germaniumdoped with n-type impurities. Alternatively, the first electrode pattern208 a may include titanium, titanium nitride, tantalum and/or tantalumnitride having a mid-gap work function. These may be used alone or in acombination thereof.

A second electrode pattern 210 a may be formed on the first electrodepattern 208 a. The second electrode pattern 210 a may have a widthgreater than that of the first electrode pattern 208 a. Further, thesecond electrode pattern 210 a may include a material having an etchingselectivity different from that of a material in the first electrodepattern 208 a. First source/drain expansion regions 212 a includingn-type impurities may be formed in the surface of the first active fin202 on both sides of the first electrode pattern 208 a. The firstsource/drain expansion regions 212 a may be partially overlapped withthe first electrode pattern 208 a.

A third electrode pattern 208 b may be formed on the second oxide layerpattern 206 b. The third electrode pattern 208 b may be intersected withthe second active fin 204. In example embodiments, the third electrodepattern 208 b may include a material substantially the same as that ofthe first electrode pattern 208 a. Further, the third electrode pattern208 b may have a second work function higher than or substantially equalto the first work function of the first electrode pattern 208 a. Forexample, when the first electrode pattern 208 a includes polysilicongermanium doped with n-type impurities, the third electrode pattern 208b may include polysilicon germanium doped with p-type impurities. Inexample embodiments, the second work function of the third electrodepattern 208 b may be higher than the first work function of the firstelectrode pattern 208 a.

In contrast, the first electrode pattern 208 a and the third electrodepattern 208 b may include titanium, titanium nitride, tantalum and/ortantalum nitride having a mid-gap work function. These may be used aloneor in a combination thereof. In example embodiments, the first electrodepattern 208 a and the second electrode pattern 208 b may have a workfunction of about 4.0 eV to about 5.2 eV.

A fourth electrode pattern 210 b may be formed on the third electrodepattern 208 b. In example embodiments, the fourth electrode pattern 210b may have a width greater than that of the third electrode pattern 208b. Further, the fourth electrode pattern 210 b may have a materialsubstantially the same as that of the second electrode pattern 210 a.Second source/drain expansion regions 212 b including p-type impuritiesmay be formed in the surface of the second active fin 204 on both sidesof the third electrode pattern 208 b. The second source/drain expansionregions 212 b may be partially overlapped with the third electrodepattern 208 b.

Although not depicted in the drawings, spacers may be arranged on bothsides of the first electrode pattern 208 a, the second electrode pattern210 a, the third electrode pattern 208 b and the fourth electrodepattern 210 b. Further, first source/drain regions and secondsource/drain regions may be formed in surfaces of the active fins onboth sides of the spacers. The CMOS FinFET in FIG. 17 may bemanufactured by any one of the above-mentioned methods.

In a method of manufacturing the CMOS FinFET, with reference to FIG. 17,a semiconductor substrate 200 having an NMOS region and a PMOS regionmay be prepared. A first active fin 202 may be formed in the NMOS regionof the semiconductor substrate 200. A second active fin 204 may beformed in the PMOS region of the semiconductor substrate 200. A firstgate insulating layer pattern 206 a may be formed on a surface of thefirst active fin 202. A second gate insulating layer pattern 206 b maybe formed on a surface of the second active fin 204. A first gate layerand a second gate layer may be sequentially formed on the first gateinsulating layer pattern 206 a and the second oxide layer pattern 206 b.The first electrode layer and the second electrode layer may bepatterned to form a first preliminary electrode pattern, a secondelectrode pattern 210 a, a third preliminary electrode pattern and afourth electrode pattern 210 b. The first preliminary electrode patternmay be intersected with the first active fin 202.

Further, the third preliminary electrode pattern may be intersected withthe second active fin 204. N-type impurities may be implanted into thesurface of the first active fin 202 exposed by the first preliminaryelectrode pattern and the second electrode pattern 210 a to form firstsource/drain expansion regions 212 a. P-type impurities may be implantedinto the surface of the second active fin 204 exposed by the thirdpreliminary electrode pattern and the fourth electrode pattern 210 b toform second source/drain expansion regions 212 b. Sidewalls of the firstpreliminary electrode pattern and the third preliminary electrodepattern may be partially removed to form a first electrode pattern 208 aand a third electrode pattern 208 b.

Spacers (not shown) may be formed on sidewalls of the first electrodepattern 208 a, the second electrode pattern 210 a, the third electrodepattern 208 b and the fourth electrode pattern 210 b. N-type impuritiesmay be selectively implanted into the surface of the first active fin202 on both sides of the spacers to form first source/drain regions (notshown). Further, p-type impurities may be selectively implanted into thesurface of the second active fin 204 on both sides of the spacers toform second source/drain regions (not shown).

According to example embodiments, the transistor may be used in asemiconductor device requiring an increased integration degree. Forexample, example embodiments may be used as a cell transistor of amemory device, e.g., a DRAM or a switching transistor of a logic device.Further, example embodiments may be used a semiconductor devicerequiring a high-capacitated transistor due to the reduced GIDL current.

The foregoing is illustrative of example embodiments and is not to beconstrued as limiting thereof. Although a few example embodiments havebeen described, those skilled in the art will readily appreciate thatmany modifications are possible in example embodiments withoutmaterially departing from the novel teachings and advantages of exampleembodiments. Accordingly, all such modifications are intended to beincluded within the scope of example embodiments as defined in theclaims. In the claims, means-plus-function clauses are intended to coverthe structures described herein as performing the recited function andnot only structural equivalents but also equivalent structures.Therefore, it is to be understood that the foregoing is illustrative ofexample embodiments and is not to be construed as limited to thespecific example embodiments disclosed, and that modifications todisclosed example embodiments, as well as other example embodiments, areintended to be included within the scope of the appended claims. Exampleembodiments are defined by the following claims, with equivalents of theclaims to be included therein.

1. A fin field effect transistor (FinFET) comprising: at least oneactive fin on a substrate; at least one gate insulating layer pattern ona surface of the at least one active fin; a first electrode pattern onthe at least one gate insulating layer pattern, the first electrodepattern being intersected with the at least one active fin; a secondelectrode pattern on the first electrode pattern, the second electrodepattern having a width greater than that of the first electrode pattern;and at least one pair of source/drain expansion regions in the surfaceof the at least one active fin on both sides of the at least one firstelectrode pattern.
 2. The FinFET of claim 1, wherein the first electrodepattern and the second electrode pattern include materials havingdifferent etching selectivities.
 3. The FinFET of claim 1, wherein thefirst electrode pattern includes polysilicon germanium, and the secondelectrode pattern includes polysilicon.
 4. The FinFET of claim 3,wherein the first electrode pattern and the second electrode pattern aredoped with impurities having a conductive type substantially the same asthat of impurities in the at least one pair of source/drain expansionregions.
 5. The FinFET of claim 1, wherein the first electrode patternincludes at least one selected from the group consisting of titanium,titanium nitride, tantalum and tantalum nitride, and the secondelectrode pattern includes polysilicon.
 6. The FinFET of claim 1,wherein the first electrode pattern has a thickness of about 100 Å toabout 400 Å.
 7. The FinFET of claim 1, further comprising: spacersarranged on both sides of the first electrode pattern and the secondelectrode pattern; and source/drain regions in the surface of the atleast one active fin on both sides of the spacers, the source/drainregions having an impurity concentration higher than that of the atleast one pair of source/drain expansion regions.
 8. The FinFET of claim1, further comprising: isolation layer patterns on the substrate on bothsides of the at least one active fin.
 9. The FinFET of claim 1, whereinthe at least one pair of source/drain expansion regions are overlappedwith an end of the first electrode pattern.
 10. The FinFET of claim 1,wherein the substrate includes a single crystalline silicon substrate, asilicon-on-insulator (SOI) substrate, a silicon germanium-on-insulator(SGOI) substrate or a germanium-on-insulator (GOI) substrate.
 11. TheFinFET of claim 1, wherein the at least one active fin includes firstand second active fins in an NMOS region and a PMOS region of thesubstrate, respectively; the at least one gate insulating layer patternincludes first and second gate insulating layer patterns on a surface ofthe first and second active fins, respectively; the at least one pair ofsource/drain expansion regions includes first and second source/drainexpansion regions, the first source/drain expansion region in thesurface of the first active fin on both sides of the first electrodepattern, the first source/drain expansion regions doped with n-typeimpurities, further comprising: a third electrode pattern on the secondgate insulating layer pattern, the third electrode pattern beingintersected with the second active fin; a fourth electrode pattern onthe third electrode pattern, the fourth electrode pattern having a widthgreater than that of the third electrode pattern; and the secondsource/drain expansion regions in the surface of the second active finon both sides of the third electrode pattern, the second source/drainexpansion regions doped with p-type impurities.
 12. The FinFET of claim11, wherein the first electrode pattern and the third electrode patternhave different work functions.
 13. The FinFET of claim 12, wherein thefirst electrode pattern includes polysilicon germanium doped with n-typeimpurities, and the third electrode pattern includes polysilicongermanium doped with p-type impurities.
 14. The FinFET of claim 11,wherein the first electrode pattern and the third electrode pattern havesubstantially the same work function of about 4.0 eV to about 5.2 eV.15. The FinFET of claim 14, wherein the first electrode pattern and thethird electrode pattern include at least one selected from the groupconsisting of titanium, titanium nitride, tantalum and tantalum nitride,and the second electrode pattern and the fourth electrode patternincludes polysilicon.
 16. A method of manufacturing a fin field effecttransistor (FinFET), the method comprising: forming at least one activefin on a substrate; forming a gate insulating layer pattern on a surfaceof the at least one active fin; sequentially forming a first electrodelayer and a second electrode layer on the gate insulating layer pattern;patterning the first electrode layer and the second electrode layer toform a first preliminary electrode pattern and a second electrodepattern, the first preliminary electrode pattern being intersected withthe at least one active fin; doping the surface of the at least oneactive fin exposed by the first preliminary electrode pattern and thesecond electrode pattern to form at least one pair of source/drainexpansion regions; and partially removing a sidewall of the firstpreliminary electrode pattern to form a first electrode pattern having awidth less than that of the second electrode pattern.
 17. The method ofclaim 16, wherein the first electrode pattern and the second electrodepattern include materials having different etching selectivities. 18.The method of claim 16, wherein the first electrode pattern includespolysilicon germanium, and the second electrode pattern includespolysilicon.
 19. The method of claim 18, wherein patterning the firstelectrode layer and the second electrode layer comprises: forming a maskpattern on the second electrode layer; dry-etching the second electrodelayer using the mask pattern to form the second electrode pattern; andwet-etching the first electrode layer under the second electrode patternto form the first preliminary electrode pattern.
 20. The method of claim19, wherein the first electrode layer is wet-etched using an etchingsolution including nitric acid, fluoric acid, acetic acid and deionizedwater
 21. The method of claim 18, wherein the sidewall of the firstpreliminary electrode pattern is partially removed by a wet etchingprocess using an etching solution that includes ammonium hydroxide,hydrogen peroxide and deionized water or nitric acid, fluoric acid,acetic acid and deionized water.
 22. The method of claim 16, wherein thefirst electrode layer includes at least one selected from the groupconsisting of titanium, titanium nitride, tantalum and tantalum nitride,and the second electrode layer includes polysilicon.
 23. The method ofclaim 16, wherein forming the first electrode pattern includes partiallyremoving the first preliminary electrode pattern to overlap the firstelectrode pattern with the source/drain expansion regions.
 24. Themethod of claim 16, wherein the source/drain expansion regions areformed by a plasma ion implantation process or tilted angle ionimplantation process.
 25. The method of claim 16, further comprising:forming spacers on sidewalls of the first electrode pattern and thesecond electrode pattern; and doping the surface of the active fin onboth sides of the spacers with impurities to form source/drain regions.26. The method of claim 25, wherein the source/drain regions are formedby a plasma ion implantation process or tilted angle ion implantationprocess.
 27. The method of claim 16, wherein the substrate includes asingle crystalline silicon substrate, a silicon-on-insulator (SOI)substrate, a silicon germanium-on-insulator (SGOI) substrate or agermanium-on-insulator (GOI) substrate.
 28. A method of manufacturing afin field effect transistor (FinFET), the method comprising: forming anactive fin protruded from a substrate; forming a gate insulating layerpattern on a surface of the active fin; sequentially forming a firstelectrode layer and a second electrode layer on the gate insulatinglayer pattern; patterning the second electrode layer to form a secondelectrode pattern, the second electrode pattern being intersected withthe active fin; etching the first electrode layer exposed by the secondelectrode pattern to form a first preliminary electrode pattern;partially removing a sidewall of the first preliminary electrode patternto form a first electrode pattern having a width less than that of thesecond electrode pattern; and doping the surface of the active finexposed by the first electrode pattern and the second electrode patternto form source/drain expansion regions.
 29. The method of claim 28,wherein the first preliminary electrode pattern and the first electrodepattern are formed by substantially the same wet etching process. 30.The method of claim 28, further comprising: partially removing asidewall of the first electrode pattern to reduce an overlapped areabetween the first electrode pattern and the source/drain expansionregions, after forming the source/drain expansion regions.
 31. A methodof manufacturing a fin field effect transistor (FinFET), the methodcomprising: forming a first active fin in an NMOS region of a substrate;forming a second active fin in a PMOS region of the substrate; forming agate insulating layer pattern on the first active pin and the secondactive pin; sequentially forming a first electrode layer and a secondelectrode layer on the gate insulating layer pattern; patterning thefirst electrode layer and the second electrode layer to form a firstpreliminary electrode pattern, a second electrode pattern, a thirdpreliminary electrode pattern and a fourth electrode pattern, the firstpreliminary electrode pattern being intersected with the first activepin and the third preliminary electrode pattern being intersected withthe second active fin; doping the surface of the first active finexposed by the first preliminary electrode pattern and the secondelectrode pattern with n-type impurities to form first source/drainexpansion regions; doping the surface of the second active fin exposedby the third preliminary electrode pattern and the fourth electrodepattern with p-type impurities to form second source/drain expansionregions; and partially removing sidewalls of the first preliminaryelectrode pattern and the third preliminary electrode pattern to form afirst electrode pattern and a third electrode pattern.